NERF

The electrochemical behavior of neural implants with 50 mum-diameter platinum electrodes was tested during acute implantations in the motor cortex of anesthetized rats. Custom Ag|AgCl reference electrodes were prepared that could be co-implanted with the probes. The results obtained in vivo are compared with in vitro measurements performed in buffered saline solution (PBS) with and without the addition of bovine serum albumin (BSA). The presence of BSA clearly altered the performance of the electrodes which was studied by means of cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), voltage transient measurements (VT) and monitoring of the open circuit potential (OCP). We found that hydrogen gas evolved at 1.22 A/cm2 in BSA-free PBS whereas in BSA-containing PBS it occurred already at 0.51 A/cm2.

Existing commercial Deep Brain Stimulation (DBS) systems are restricted by their limited electrical stimulation selectivity and open-loop approach. As a step towards a closed-loop clinical DBS system we develop silicon-based multielectrode neural probe arrays for in vivo selective neuronal recording and stimulation. This paper reports the fabrication and subsequent evaluation of a planar neural probe containing an array of 8 Pt contacts with diameters of 50um. The probe was designed to provide Magnetic Resonance Imaging (MRI) compatibility. The recording selectivity of the probes was tested in acute electrophysiological experiments in the motor cortex of anesthetized rats (n=9). Obtained recordings of action potentials of single neurons demonstrated an acceptable level of interference with the brain function. The in vivo MRI compatibility of the probes was validated in a chronic implantation study in rats (n=3; 3 weeks follow-up). The animals did not show signs of pain or distress or other types of abnormal behavior. Obtained results demonstrate the usability of the neural probe both as a prototype of a medical device and as a research tool in fundamental neurophysiological studies.

Since a few decades, micro-fabricated neural probes are being used, together with microelectronic interfaces, to get more insight in the activity of neuronal networks. The need for higher temporal and spatial recording resolutions imposes new challenges on the design of integrated neural interfaces with respect to power consumption, data handling and versatility. In this paper, we present an integrated acquisition system for in vitro and in vivo recording of neural activity. The ASIC consists of 16 low-noise, fully-differential input channels with independent programmability of its amplification (from 100 to 6000 V/V) and filtering (1-6000 Hz range) capabilities. Each channel is AC-coupled and implements a fourth-order band-pass filter in order to steeply attenuate out-of-band noise and DC input offsets. The system achieves an input-referred noise density of 37 nV/√Hz, a NEF of 5.1, a CMRR >; 60 dB, a THD <; 1% and a sampling rate of 30 kS/s per channel, while consuming a maximum of 70 μA per channel from a single 3.3 V. The ASIC was implemented in a 0.35 μm CMOS technology and has a total area of 5.6 × 4.5 mm2. The recording system was successfully validated in in vitro and in vivo experiments, achieving simultaneous multichannel recordings of cell activity with satisfactory signal-to-noise ratios.

We used reciprocal derivative chronopotentiometry (RDC) with platinum electrodes of 50 μm diameter in 0.15 M phosphate buffered saline solution to identify the various electrochemical processes occurring at the electrode during biphasic current pulsing. RDC allowed to determine the limits of water hydrolysis based on the specific (dt/dE)-E data representation employed in this technique resulting in curves similar to the voltammetric i-E response. Current stimulation was performed by either varying the pulse amplitude or pulse width. We found that the limits for H2 and O2 evolution for constant-amplitude pulses lied at 0.51 mC/cm2 and 0.67 mC/cm2, respectively, while for constant-width pulses they occurred at slightly lower values of 0.49 mC/cm2 and 0.61 mC/cm2, respectively. We could also extract values for the anodic and cathodic overvoltages associated with gas evolution. The cathodic overvoltage for H2 evolution was 1.43 V for both constant-amplitude and constant-width pulses, while the anodic overpotentials for O2 evolution were 2.45 V in the first and 2.24 V in the latter case. These values are clearly larger than the gas evolution limits generally found with steady-state voltammetry.

Different cholinomimetics are used in conditions of CNS acetylcholine (ACh) deficit. In this study, we examined the effect of the acetylcholinesterase inhibitor galanthamine in a prolonged alcohol intake model of ACh deficit in male Wistar rats. After 16 weeks of alcohol intake and a 2-week pause, rats administered galanthamine (2.5 mg/kg/day i.p.) showed an improved speed of learning and short-term memory in the shuttle box test as compared to the saline-injected alcoholic group (p &amp;lt; 0.05). Four weeks later, significant improvement in the passive avoidance memory of alcoholic galanthamine-treated rats was noted in the eight-arm radial maze (14 day test duration) as compared to the saline-injected alcoholic group (p &amp;lt; 0.05). During the first week in the shuttle box test, the nonalcoholic galanthamine-treated animals exhibited significantly impaired performance as compared to the untreated nonalcoholic control, while four weeks later, in the eight-arm radial maze, both groups did not differ. Our results show that galanthamine improves the speed of learning, short-term memory and spatial orientation of rats in conditions of prolonged alcohol intake.

In this study the effect of dexamethasone on the motoneuronal cell death and the nuclear and somatic morphology changes occurring after peripheral nerve transection in the neonatal rats has been determined. The study was performed on 3 day old Wistar rats. Animals were divided into 3 groups--control, axotomised, and axotomised and dexamethasone-treated. The nerve transection was performed bilaterally. A dose of 0.5 mg/kg/24h dexamethasone, administered i.p., was used. On day 7 after the operation the animals were sacrificed and the motoneurons in segments L4 and L5 in the spinal cord were counted and their morphology was analysed. 25. 88% cell loss was found in the axotomised group (p&amp;lt;0.001 vs. control) versus 43.33% cell loss in the dexamethasone-treated and axotomised animals (p&amp;lt;0.01 vs. control). Dexamethasone significantly decreased the number of the surviving motoneurons (p&amp;lt;0.05 vs. axotomised). The axotomised group showed enlargement of the somatic area and the maximal and minimal diameters of the cell while the dexamethasone-treated and axotomised group showed soma shrinkage and decrease in the minimal cell diameter. Our results propose a possible hazard towards the application of dexamethasone in the treatment of new-borns with concomitant nerve injuries.

Neuroanatomy is the study of the anatomical organization of the brain. Reciprocal communication between the brain and the cardiovascular system is important in sustaining neurobehavioral states that allow organisms to cope with their environment. Furthermore, ...

Spatial distribution of motor endplates affects the shape of the electrical activity recorded from muscle. In order to provide information for realistic models of action potential propagation within muscles, we assembled three-dimensional maps of the motor endplates of the rat medial gastrocnemius (MGM) and lateral gastrocnemius (MGL) muscles. The maps were assembled from histological cross sections stained for acetylcholinesterase activity. Within MGL, the motor endplates formed three columns along its longitudinal axis. Within MGM, the motor endplates were arranged in a leaf-like body that shifted obliquely from proximal to distal. As inferred from the proximo-distal distribution of the cross-sectional projection area, the majority of the motor endplates were concentrated in the middle of MGL and in the distal third of MGM. Regions of maximal motor endplate concentration are considered most suitable for injections of neuroactive substances, such as neuronal tracers. The assembled maps of the gastrocnemius muscles can be used as guides for such injections within the motor endplate zones.